In the past, fabric conditioning has been carried out either during the rinsing step of a fabric washing and rinsing process or during tumble drying of the fabric. In almost all cases rinse conditioning is accomplished by adding a liquid dispersion of a rinse conditioning agent to the rinse liquor. The liquid dispersion was traditionally distributed and made available to consumers as a ready-to-use aqueous dispersion. More recently, concern for the environment and consumer convenience has led to the sale of concentrated aqueous dispersions which are either used in smaller amounts or are mixed with water to form a predilute before use as described in Turner, U.S. Ser. No. 08/053,588.
In EP 234082 it has been proposed to supply rinse conditioner as a solid block. This approach requires the use of a special restraint for the block and may also require the modification of the washing machine to enable the block to be dissolved and dispensed by a spray system.
Various proposals have been made to supply fabric softener in granular or powdered form. EP 111074 is typical and uses a silica to carry the softener. A disadvantage of using a carrier such as silica is that it bulks up the product and serves no function beyond making the powder compatible with other ingredients that may be contained in a washing powder.
WO 92/18593 describes a granular fabric softening composition comprising a nonionic fabric softener and a single long alkyl chain cationic material. The specification teaches that effective cationic softening compounds when used in granular form exhibit poor dispersion properties. Moreover, this publication states that the dispersibility problems of powders should be overcome by replacing the cationic softening compound with any number of nonionic softening compounds. Softening is maintained by the nonionic softening compound and the problem of dispersing the cationic compound as a powder is dismissed because less cationic material is used.
For these reasons, despite the obvious environmental and transport-saving advantages of selling a water-free powdered rinse conditioner, manufacturers have not done so.